Update System - Best practice

[eluser]vlados2[/eluser]
Hi,
I am new to the community and hello to all I am sure I will spend a lot of time here

So My first post will be to discus the best practices of building an auto update module/update server.
Is it better to build an application with core and additional modules and update the core (like wordpress) or to build each file and track changes (somehow ) like a SVN, or to build a module to download the latest changes from the SVN

What you think?